Domestic clothes drier with twin fan

ABSTRACT

Dryer with a drum ( 1 ) where the clothes must be placed, one fan ( 5 ) blowing a drying air current through such drum, a condenser ( 3 ) in which such drying air current enters, a cooling air duct ( 4 ) blowing a second fresh air current through the condenser, produced by a second fan ( 6 ) connected to the air duct; at least one of these fans is composed of one set of external blades ( 10, 11, 12 ) and a second set of internal blades ( 21, 22, 23 ) that spin on a common axle (X), and the blades of the first set are laid out along one cylindrical structure, while the second set of blades are laid out along a second cylindrical structure inside the first one.

The present invention relates to an improved type of clothes drying machine, preferably of the domestic kind, which operates in a particularly efficient manner.

In the continuation of the present description reference will be made to a simple clothes dryinq machine, but it is understood that the above explanation may also be applied in an identical manner to—and therefore is also valid for—a combined washing and drying machine.

Clothes drying machines which operate using different methods are known, in particular those operating by means of condensation of a flow of hot air which is blown into the drum and which removes the moisture contained in the clothes or by discharging externally said flow of moist hot air.

Said clothes drying machines are described generally in the European Patent Application No. EP 04 009650.5, in the name of the same applicant, to which, for the sake of brevity, reference should be made.

However, in order to assist the reader, a short descriptive part of said document is included here.

As is well-known, these machines are made by installing a heating and ventilation system, normally a ventilator consisting of a fan and associated electric motor, which draws the air from the outside and by means of suitable ducts heats it and blows it into the drum containing the clothes to be dried.

A heating element is installed inside said duct and, suitably activated, heats the air which passes over it and is blown in by said ventilator, so that hot air is introduced into the drum so as to cause evaporation of the moisture contained in the clothes.

After being introduced into the drum, the hot air causes evaporation of the moisture contained in the clothes and therefore is practically saturated or completely saturated with it; said air is then propelled by said ventilator, creating a continuous flow which is directed into a suitable condensation device, usually consisting of a heat exchanger which is passed through, along the so-called “hot” path, by said moist hot air flow and, along the so-called “cold” path, by a substantially continuous flow of air drawn from the environment and introduced back into the environment after passing through said exchanger.

Conventionally, said air flow along the “cold” path is also activated and maintained by a ventilator operated by a respective electric motor.

Said clothes drying machines are fairly simple, low-cost and operationally reliable machines, but, as is well-known, they have the common drawback that they are significantly noisy owing to the air flow which is blown in at a considerable rate inside the suction and discharge ducts.

Consequently, the use of these machines is normally limited to certain periods, this making their use less attractive for the average user.

The most immediate technical solution for achieving the circulation of said two separate air flows is that of using respective ventilators inserted inside the corresponding ducts and operated by respective motors which are controlled independently.

Obviously said two ventilators use a not insignificant amount of power, owing to, not only mechanical friction factors which, however, are of limited importance, but also and in particular the power which must be used in order to impart to the respective air flows the desired speed, or pressure, at the necessary flowrate.

It would therefore be desirable, and this is the main object of the present invention, to provide a clothes drying machine of the condensation or externally discharging type, which is provided with fans for drying and if necessary cooling the condenser and is able to offer a normal drying performance, but which is significantly more efficient, without increasing the complexity of the machine, while keeping the production costs low.

These and other objects which will be described further below are achieved by providing a clothes drying machine according to the claims which follow; the invention will be understood more clearly from the following description, provided solely by way of a non-limiting example with reference to the accompanying drawings, in which:

FIG. 1 shows a general schematic diagram of a clothes drying machine provided with a condenser and two fans which are rigidly connected together, according to the prior art;

FIGS. 2 and 3 show two perspective views, i.e. a front view and side view, respectively, of a fan for circulating air in a machine according to the invention;

FIG. 4 shows a front view of the said fan;

FIG. 5 shows a cross-sectional view through the centre of the said fan;

FIG. 6 shows a front view of a variant of embodiment of the fan according to the invention;

FIG. 7 shows, in a same diagram, two: separate graphs illustrating the progression of the pressure and electric power consumption of the motor in a clothes drying machine with a fan according to the prior art (graph A) and with a fan which is the same, but equipped with the present invention (graph B), respectively.

With reference to FIG. 1, in a clothes drying machine according to a preferred embodiment of the invention, a drum 1 is provided for containing the clothes to be dried and has, associated with it, a duct 2 for circulation of the drying air; the latter also passes through a condenser 3 which is able to condense the moisture present in the air passing through it, said condenser being passed through by a “cold” air flow, namely one which is drawn from the environment and conveyed to the said condenser 3 via an associated duct 4.

Both the ducts 2 and 4 contain inside them two respective fans 5, 6 for actuating the respective drying and cooling air flows.

One of said fans, or both of them, consist of two sets of vanes which are arranged on the outer surface of a respective cylindrical form, said two cylindrical forms being understood in the non-material sense.

Said cylindrical forms are moreover coaxial and the radius of a first cylindrical form is smaller than the radius of the second cylindrical form.

Essentially the two cylindrical forms, and therefore also the two sets of vanes, are inserted inside one another, without touching however, as is clearly illustrated in FIGS. 2 to 5.

The vanes 10, 11, 12 . . . of the first set, or outer set, are rigidly supported by a wall “P” arranged along a geometric base of the respective cylindrical form, and the supporting structure of said fan is thus formed.

Advantageously the vanes of the set of inner vanes 20, 21, 22 . . . of the second set are likewise supported on said wall “P” such that the vanes of both sets are joined together and can rotate in synchronism.

Still with reference to FIGS. 2, 3 and 4, in order to avoid damaging vortices on the inner vanes, advantageously the latter have a shape which is not flat but curved, i.e. with the associated concavities C1, C2, C3, etc., directed in the sense of rotation.

Moreover and preferably the free ends of the vanes of each set are connected by a respective reinforcing ring 7, 8.

The fan according to the invention is thus formed.

The mode of operation of this fan will now be clear: in fact the air which is sucked in by the cavity between the two sets of vanes is forced outside by the outer vanes in accordance with known mechanical principles, while the air sucked inside the inner vanes is naturally blown outwards, i.e. into said cavity, with a certain given speed which is added to the speed imparted by the outer vanes through which it passes immediately afterwards.

Basically operation similar to that of a twin-stage fan occurs, in which at least part of the air sucked in is subject to the series action of the vanes of the two sets.

Obviously the flow of said air blown from the inner vanes also assists the movement of the air sucked directly from the outside into said cavity, this favouring the general efficiency of the fan.

It may also be considered that the air blown out from the set of inner vanes is slightly slowed down by the air sucked in directly from the outside into said cavity; however, the overall effect is an improvement in the efficiency of the fan, as demonstrated by FIG. 7, which shows two graphs illustrating the flowrate of a fan with and without the invention, the graph A showing the pressure and the consumption of a fan without the invention and the graph B showing the corresponding parameters of the same fan to which the set of inner vanes according to the invention has been added.

With reference to FIG. 4, it has also been observed that in certain embodiments and in certain operating conditions, for example when the fan must operate always in the same direction of rotation, or, as more frequently occurs in a clothes drying machine, in a main direction of rotation, the efficiency of the fan is further increased if the inner vanes are provided with an orientation which is not radial, but inclined at a given angle “i” with respect to the radial plane which passes through the latter, and in particular if said inner vanes are inclined such that, taking as a reference the direction of rotation “S” of the fan, the outer edges 45, 46, 47 of each inner vane are situated further forwards than the respective inner edges 45A, 46A, 47A, obviously relative to the planes p1, p2, p3 which pass through said respective vanes.

However, more generally it is possible to envisage fans which are operated in an alternating manner and for identical periods in each direction of rotation; in this case it is obviously advantageous if the vanes of the fan also do not have preferential forms, but on the contrary, as shown by way of example in FIG. 6, all the inner vanes are flat and arranged radially. 

1. Clothes drying machine or combined clothes washing and drying machine comprising a drum (1) containing the clothes to be dried, at least one first fan (5) able to blow a first flow of drying air through said drum, optionally a condenser (3) inside which said drying air flow is made to pass and an associated cooling air duct (4) which conveys a second flow of fresh air through said condenser (3), said second flow being actuated by a second fan (6) associated with said air duct (4), characterized in that at least one of said fans (5, 6) is formed by means of a first set of outer vanes (10, 11, 12) and a second set of inner vanes (21, 22, 23) rotating with respect to a common axis (X), in that the vanes of the first set of vanes are distributed on a first cylindrical form, and in that the vanes of the second set of vanes are arranged along a second cylindrical form which is different from the first cylindrical form and are arranged inside said first cylindrical form.
 2. Machine according to claim 1, characterized in that a base of the cylinder which is defined by the first set of vanes is at least partly closed by a wall (P).
 3. Machine according to claim 2, characterized in that the vanes of the second set of vanes arranged internally are fixed at one of their ends to said wall (P).
 4. Machine according to any one of the preceding claims, characterized in that said vanes of said first set are radial with respect to said common axis (X).
 5. Machine according to claim 4, characterized in that said vanes of the second set of inner vanes (20, 21, 22) are oriented in a non-radial direction with respect to said common axis and have a given inclination (i) with respect to the respective radial planes passing through them.
 6. Machine according to claim 5, characterized in that said given inclination is such that the outer edges (45, 46, 47) of respective inner vanes are situated further forwards than the respective inner edges (45A, 46A, 47A).
 7. Machine according to any one of the preceding claims, characterized in that said inner vanes have a concave surface (C1, C2, C3) directed in the sense of rotation of said fan. 